The present invention relates to a control and compensation device in an anti-skid control system which is actuated so as to immediately release the braking force of wheels only for a predetermined period of time. The present invention takes the place of the controlling operation of a conventional anti-skid control system, when the wheels are in a locked state continuously for more than a predetermined time as a result of the condition that the antiskid control system for a vehicle including a main control circuit for producing anti-skid control signals to control the braking force of the wheels is out of order for one reason or another, by detecting such a locked state.
Trouble modes of the anti-skid control system considered, include the following two types: a first type is the trouble wherein the braking force does not at all exert on the wheels, and a second type is the trouble wherein the braking force exerts on the wheels but the anti-skid function is lost. In the past, in particular, importance is attached to the aforementioned first type of the trouble. It has been usual that when the first type of trouble occurs, the power supply of the anti-skid control system is immediately cut off to stop the anti-skid function and to thereby assume the same state as the second type of trouble. On the other hand, when the second type of the trouble occurs, an alarm is merely given.
Generally, there is a significant difference between the braking sense when the anti-skid function is exercised and the braking sense when the anti-skid function is not exercised. Particularly, in a vehicle in which the braking force of a plurality of or all wheels is controlled by a single anti-skid control system, in the event that the anti-skid function is rapidly stopped due to the trouble of the anti-skid control system, it is extremely difficult for a driver, who is wholly accustomed to an ordinary braking sense, to rapidly follow the braking sense so that a great braking force is exerted on each of wheels in the ordinary braking sense. As a consequence, each wheel tends to assume a locked state, thus posing various inconveniences in driving the vehicle.
In order to minimize the disadvantages noted above, there is provided an anti-skid brake device wherein a plurality of anti-skid control systems actuated independently each other are provided one on each of wheels so that even if either of the anti-skid systems is out of order, no influence would be exerted on the anti-skid function of wheels other than the wheel corresponding to the disordered anti-skid control system. In this case, however, if the anti-skid control systems corresponding to the rear wheels are out of order, it is likely that anti-skid function is applied to only the front wheels whereby the front wheels are not locked but only the rear wheels are locked. If such a state should occur, the running of the vehicle becomes extremely unstablized to cause an abrupt whirl. This is more of a dangerous state than in the case where all wheels are locked.